EP1020454 describes polymorphic forms A, B, C, D and G of febuxostat as well as process for their preparation by crystallization of febuxostat in a methanol/water mixture, depending on concentration and temperature conditions. The process also includes the preparation of an amorphous form. The six different polymorphs may be produced using the same phase diagram.
However, by performing different assays the authors of the present invention have found that the preparation of form A according to the processes described in EP1020454 is hardly reproducible and, in addition, contamination of other forms may occur or undesired forms may be obtained.
Thus, there is a need to develop a process for preparing the crystalline form A of febuxostat that is capable of providing a good yield and high purity.